File Transfer Protocol (FTP) is a universal protocol used to transfer files between an FTP server and an FTP client, and is described in detail in RFC 959. FTP can be applied in a stack system. The stack system refers to a system consisting of multiple chassis devices (called “chassis” for short). In the stack system, one chassis is selected as a master chassis according to a preset selection principle, and the other chassis are regarded as slave chassis. An FTP server master process runs on the master chassis, and an FTP server slave process runs on one of the slave chassis.